SECT, i CRYPTOGAMS 425 



spores. Only in one order, Anthocerotaceae, does the capsule have a 

 columella, or an axial mass of sterile cells, which also conduct the 

 metabolic products to the developing spores. 



2. Musci (Mosses). The protonema of the sexual generation is 

 usually well developed and distinctly defined, and the moss plant is 

 always segmented into stem and leaves. The leaves are arranged 

 spirally in polysymmetrical, less frequently in bisymmetrical, rows. 

 The capsule is always without elaters, but, except in one genus, it 

 always possesses a columella. 



CLASS I 

 Hepaticae (Liverworts) ( 97 ) 



The Hepaticae are divided, according to the structure of the 

 sporogonium and the segmentation exhibited by the sexual generation, 

 into five orders : the fiicciaceae, Marchantiaceae, and Anthocerotaceae, 

 comprising exclusively thalloid forms, the Jungermanniaceae, including 

 both thalloid and dorsiventral foliose forms, and the Calobryaceae, 

 which are radially constructed foliose forms. 



Order 1. Ricciaceae ( 98 ) 



Of all the Hepaticae, this order exhibits the simplest structure. The genus Iticcia 

 belongs to this order ; its clichotomously-lobed or cleft thallus forms small rosettes, 

 and grows on damp or marshy soil, llicria tmtans is found floating, like Duckweed, 

 on the surface of stagnant water. 

 Riccia fiuitans, on the other ham I. 

 lives wholly submerged, and has 

 narrow, more profusely branching, 

 thalloid segments (Fig. 379); it can, 

 however, grow on marshy soil, and 

 then forms flat rosettes. The Riecias 

 are provided with fine rhizoids 

 springing from the Under side of 

 the thallus, and possess, in addi- 

 tion, a row of transversely disposed ,, I(] y!>\-Ricda fluit ,>.x. J,.Sul.i.i.>rt,"-<l floating form ; 

 ventral scales, consisting of a single /;, land form. (Nat. siw. K, after GOEBEL.) 



layer of cells, which also function 



in the absorption of nourishment. Both organs are wanting in the submerged 

 form of Riccia fluitans. 



The antheridia and archegonia are sunk in the surface of the upper side of the 

 thallus. From the fertilised egg-cell is developed a spherical sporogonium which 

 has no stalk. The wall of the sporogonium consists of a single layer of cells ; it 

 becomes disorganised during the ripening of the spores, which are eventually set 

 free by the rupture and disintegration of tin; venter and the surrounding cells of the 

 thallus. 



